The invention relates to a programmable field measuring instrument.
Field measuring instruments which measure a process variable in a process sequence are often used in automation and process control technology. Field measuring instruments for determining flow rate, filling level, differential pressure, temperature, etc., are generally known. In order to acquire the corresponding process variable, mass flow or volumetric flow, filling level, pressure, temperature, etc., the field measuring instruments must be arranged in direct proximity to the relevant process component. The field instruments each generate measurement signals which are a measure of the acquired process variable. The measurement signals are forwarded to a control center or a control system. As a rule, the entire process control takes place from the control center, where the various measurement signals from different field measuring instruments are evaluated and, on the basis of the evaluation, control signals are generated for field instruments (actuators) which control the process sequence. The signal transmission between field measuring instrument and control center, is effected e.g. via a current loop or via a digital databus.
More and more programmable field measuring instruments are being used in addition to analog field measuring instruments. ASICs (application-specific integrated circuits) and SMDs (surface mounted devices) are often used for this purpose.
In the case of programmable field measuring instruments, more and more xe2x80x9cintelligencexe2x80x9d is being displaced into the field to the actual measurement location.
This means that different functionalities are possible on site; for example, the way in which the measurement data are stored may vary, the correction of measurement data on the basis of calibration factors may be done in different ways, the measurement data acquisition and measurement data evaluation may be different, additional regulating and actuating functions may be built in, the signal transmission to the control center may vary, and there may also be different ways of providing self-monitoring of the field measuring instrument (predictive maintenance). The field measuring instrument no longer communicates just a simple measurement signal, but rather an already conditioned measurement signal and possibly further additional information as well to the control center or to other field measuring instruments.
The sum of these possibilities mentioned above makes up the functionality of the field measuring instrument. A corresponding control program (software) is necessary for each functionality. This control program is normally stored in a nonvolatile memory in the sensor. Consequently, the functionality of a field measuring instrument depends to a critical extent on the control program which, as a rule, is made available by the manufacturer of the field measuring instrument. Such a control program may encompass certain basic functions (basic functionality) or extended functionalities as well.
The control program is normally implemented during the production of the field measuring instrument. In other words, the functionality of the field instruments is thus fixedly predetermined after the latter has been produced, and cannot be changed in a simple manner. To do so would require reprogramming, that is to say a change to the control program in the field measuring instrument. Such reprogramming of a field measuring instrument is very complicated, however. Another possibility of effecting the change is to exchange the memory holding the old control program for a memory holding a new control program on site. To that end, the housing of the field measuring instrument must be opened and the memory exchanged manually, by a service engineer. During this time the voltage supply of the field measuring instrument is, of course, switched off and measurement signals cannot be transmitted to the control center. If the field measuring instrument is connected to the control center via a digital databus, then the field instrument must be reinitialized, after the memory has been exchanged, on the databus. A further possibility for effecting reprogramming consists in connecting the field measuring instrument e.g. to a portable personal computer (e.g. laptop) and xe2x80x9cplaying inxe2x80x9d the new control program. This requires a reprogrammable memory in the field measuring instrument. These possibilities are relatively complicated and in both cases the acquisition of the process variable is interrupted for a relatively long time. A further possibility would consist in already storing different control programs during the production of the field measuring instrument, and in selecting the desired control program on site. This could be done e.g. using a simple microswitch. Since program development causes considerable costs, depending on complexity and scope, field measuring instruments with different functionalities differ in price, among other things. A simple solution using a microswitch is not able, therefore, to preclude misuse, that is to say the selection of a control program without authorization.
EP-B 0537738 xe2x80x9cMethod of protecting computer software . . . xe2x80x9d and EP-A 0940 743 xe2x80x9cCompact transparent dongle devicexe2x80x9d each disclose software protection devices and corresponding methods. These known software, protection devices are normally connected to the parallel interface of the personal computer (PC) used. The user calls up a specific program e.g. via a Windows interface and the selected program identifies whether or not the software protection device needed for authorization is present. Only if the required software protection device is present is the selected program executed properly, otherwise the program is terminated. In this case, however, the program selection is effected manually by the respective program user.
The object of the invention is to provide a programmable field measuring instrument which prevents unauthorized use of functionalities.
This object is achieved by means of a programmable field measuring instrument having a control unit, which serves for executing a control program and which has, as an interface, a connector terminal, which is connected, in a manner that allows it to be released, to a software protection device essentially comprising a connector mating element with an integrated electronic component, which allows authorization examination by the control unit.
In a preferred embodiment of the invention, the electronic component comprises a microcontroller whose control program memory is protected or can be protected against read-out.
In a preferred embodiment of the invention, the electronic component comprises a peripheral interface controller.
In a preferred embodiment of the invention, the update terminal of the field measuring instrument is used as the connector terminal.
In a preferred embodiment of the invention, the control unit comprises a microprocessor.
Furthermore, the invention comprises a method for the protection of software in a field measuring instrument having a control unit and a memory with different control program variants, having the following method steps:
start of an initialization routine of the control unit,
interrogation of the identifier of a software protection device connected, in a manner that allows it to be released, to the field measuring instrument,
selection of a control program variant by the control unit on the basis of the identifier.
In a preferred embodiment of the invention, with the interrogation, a random quantity Z generated in the control unit is sent to the software protection device. From said random quantity, new values X1=F1(Z) and X2=F2(Z) are calculated in each case according to an algorithm in the control unit and in the software protection device and are compared with one another in the control unit. In the absence of correspondence X1xe2x89xa0X2, a program stop is effected.
In a preferred embodiment of the invention, the identifier is transmitted with the result value of the algorithm, said result value having been calculated in the software protection device, and is evaluated in the control unit.